The All Blacks have been handed a major boost ahead of their crucial World Cup opener against the Springboks.

After missing out on the All Blacks' final warm-up test against Tonga last weekend with a minor shoulder issue, Richie Mo'unga looks set to be available for the first match of the tournament in Japan, with assistant coach Ian Foster confirming the first-five should be "fully fit and available".

Steve Hansen and co. were forced to play Beauden Barrett back at No 10 for the Tonga clash for the first time since their narrow win over Argentina in July, with Ben Smith slotting back into fullback.

But the defending world champions now look set to revert back to the Mo'unga/Barrett dual playmaker combination against the Springboks.

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"Last week we sort of said we pulled him out more precautionary, so this week's about him graduating back into full training," Foster told reporters on Wednesday.

"He's tracking really, really well."

Richie Mo'unga. Photo / Photosport
Richie Mo'unga. Photo / Photosport

Foster was confident that Mo'unga will be ready to go in the clash at International Stadium Yokohama a week from Saturday.

"[We] expect him to be fully fit and available," he said.

Foster also said the All Blacks are looking forward to facing one of the pre-tournament favourites first.

"We love the draw because it's meant that we've turned up and there's no excuse, no waiting around ... it's right there in front of us," he said.

"We're about to face a very confident South African team but they're going to face a very determined All Black team and it's a great way for the tournament to get under way."